Pedro M. Leunda

River channelization effects on fish population structure in the Larraun river (Northern Spain)

As a consequence of the construction of the A-15 highway between 1991 and 1995, some modifications affecting the Larraun River (Navarra, North of Spain) were made. One of the most important effects was the channelization of a section of the river in the middle zone. Fish were caught by electrofishing in August of 1996 in the channelized reach, as well as in non-modified stretches upstream and downstream. Physical and chemical variables and shelter availability were also analyzed. The captured fish were measured (total length) and released into the river. We calculated the density, biomass, length distribution and diversity, comparing the obtained results from the different stretches. The number of species was higher in the lower zones of the river and diversity increased progressively downstream. The fish density in the channelized section was slightly lower than in the other two points. Also biomass in the channelized section was about a factor of 10 smaller than the calculated biomass in unaltered points. Moreover, in comparison with the unaltered sections of the river, in the channelized area a major decrease in the presence of fish larger than 150 mm was detected. The low shelter availability in the channelized section, lack of bank vegetation and alterations in the substratum could explain the observed variations in the length distribution, biomass and the lower value of the density of European minnow, Phoxinus phoxinus (Linnaeus, 1758).

Threatened fishes of the world: Siphateles bicolor snyderi (Miller, 1973) (Cyprinidae)

Pedro M. Leunda, Rafael Miranda, Javier Madoz, Steve Parmenter, Yongjiu Chen & Bernie May Department of Zoology and Ecology, University of Navarra, Apdo. 177, E-31080 Pamplona, Navarra, Spain (e-mail: pleuurr@alumni.unav.es) California Department of Fish and Game, 407 West Line St., Bishop, CA 93514, U.S.A. Genomic Variation Lab., Department of Animal Science, University of California, Davis, CA 95616, U.S.A.

Bone-to-Body Biometric Relationships for Owens and Lahontan Tui Chubs and their Hybrids in California

Abstract Regression parameters for the length of several bony structures against fish body length, and for body length against body weight, were determined for Owens tui chub Siphateles bicolor snyderi, Lahontan tui chub Siphateles bicolor obesa, and hybrid swarm deriving from the two species. Two-hundred eleven individuals from 16 localities from the Owens River and neighboring basins along the border between California and Nevada were used for regression analyses. The coefficient of determination of linear regressions for scales, pharyngeal arches, dentaries, cleithra, and opercula against body length were consistently high (r2 ≥ 0.9). Differences between subspecies were mainly with reference to the intercept parameter in comparisons involving Lahontan tui chub. Coefficients of determination from log-linear length–weight regressions were also high (r2 ≥ 0.9) for individual taxa and for the pooled data set combining both Lahontan and hybrid species. The length–weight relationship did not differ between s...

Threatened fishes of the world: Barbus haasi (Mertens 1925) (Cyprinidae)

barbel not reaching the rear edge of the eye. Last unbranched ray of the dorsal fin with small denticles. Anal fin is long and caudal peduncle is short and high. Body presents dark blotches. Part of caudal, anal and pelvic fins are red. Drawing by Rafael Miranda. Distribution: Most headwater streams of the Ebro River Basin and North Mediterranean rivers of the Iberian Peninsula. Abundance: Restricted to headwaters and occasionally in middle reaches of streams, scarce where present. Habitat and ecology: This benthonic species prefers upper reaches of rivers, with high flow and clear, cold waters. Barbus haasi occurs in rocky and vegetated areas and feeds on macroinvertebrates (mainly Chironomidae, Ephemeroptera and Trichoptera). Reproduction: The spawning period extends throughout April and June, related to periods of high stream flow. Fecundity ranges from 2000 to 7000 eggs per female. The males have an early maturity (one year) and grow more slowly than females. The females live for 8 years while the males only live for 7 years. The females have multiple spawning, releasing two to five egg batches depending on their size, such that largest females spawn more batches than the small ones (Aparicio & Sostoa 1998). Threats: The species is threatened by invasive alien fish species (mainly piscivores) and habitat loss due to water abstraction, construction of small dams, stream desiccation, etc. Anthropogenic water pollution is another important disturbance factor. This endemic species of the Iberian Peninsula is currently in rapid decline because the above noted impacts are intensified by the characteristic irregularity of the Mediterranean rivers. Conservation action: None. Conservation recommendations: Waste water and water pollution control and treatment. Correction of the impact of stream regulation by water releases to simulate natural flow patterns. Prevent alien fish species introductions and eradication of the existing alien species which impact on B. haasi. Habitat protection and control of invasive alien fish species are the main actions necessary to prevent the further decline of Barbus haasi. Remarks: There has been some controversy with regard to the systematic position of

Morphometric Contribution to the Detection of Introgressive Hybridization in the Endangered Owens Tui Chub in California

AbstractThe Owens Tui Chub Siphateles bicolor snyderi has become endangered by introgressive hybridization with the Lahontan Tui Chub S. bicolor obesa since the 1960s. Adequate conservation strategies require prior identification of pure populations, which is usually difficult because the diagnostic features presented in the formal subspecies description do not always allow unequivocal determination of populations. In the present study, the shape and some meristic features of the scales, along with the shape of other bones with taxonomic value, were analyzed to distinguish both parental subspecies and their hybrids in samples diagnosed in a previous work using microsatellite DNA. Scales, pharyngeal arches, dentaries, cleithra, and opercula of 211 individuals from 16 localities across the Owens River and neighbouring basins in California and Nevada were compared. The results show that the meristic parameters of the scales were in agreement with values provided by Miller (1973) for the parental subspecies. ...